Currently, resonance devices using a MEMS (Micro Electro Mechanical Systems) technique are used as a timing device, for example. These resonance devices are typically mounted on a printed circuit board that is incorporated into an electronic device such as a smartphone. In general, these resonance devices include a lower substrate, an upper substrate that forms a cavity between the lower substrate and the upper substrate, and a resonator that is disposed within the cavity between the lower substrate and the upper substrate.
For example, Patent Document 1 (identified below) discloses an out-of-plane bending resonator having a plurality of vibration arms. In the exemplary resonator, each vibration arm is connected at a fixed end thereof to a front end of a base portion, and the base portion is connected at a rear end thereof, which is opposite to the front end thereof, to a support portion. For example, the support portion is connected to a base that is interposed between the lower substrate and the upper substrate. In the example of FIG. 1 of Patent Document 1, since electric fields to be applied to the vibration arms are set in directions opposite to each other, vibrations in opposite phases are achieved between an inner vibration arm and outer two vibration arms.
Patent Document 1: Japanese Patent No. 5071058.
In the resonance device as disclosed in Patent Document 1, the resonant frequency is adjusted, for example, by adjusting the film thicknesses of materials forming the resonator when the resonator is manufactured. However, when the resonant frequency is adjusted in this way, the adjusted resonant frequency fluctuates by a load being applied to the resonator due to heat or stress in a subsequent step for the production.